The influence of habitat homogenization on the trophic structure of fish fauna in tropical streams

Habitat homogenization is one of the most important drivers of change in riverine fauna. Therefore, the aim of this study was to determine whether habitat homogenization influences the trophic structure of fish assemblages in tropical streams. We sampled 78 streams located in pasture and crop lands to examine habitat variables and fish. Principal coordinates analysis, canonical analysis of principal coordinates, and a distance-based test for homogeneity of multivariate dispersions revealed two groups of streams, designated homogeneous and heterogeneous, based on the habitat variables. We determined trophic guilds according to the frequency and biovolume of food items. Seven guilds were identified: aquatic insectivores, terrestrial insectivores, detritivores, herbivores, omnivores, algivores, and detritivores-algivores. Homogeneous streams showed higher abundance and biomass of aquatic insectivores, detritivores, and algivores. Heterogeneous streams showed greater diversity of trophic guilds and higher abundance and biomass of terrestrial insectivores and herbivores than homogeneous streams. Our results demonstrate that trophic structure is influenced by habitat condition. Additionally, the riparian canopy and nearshore vegetation have a modulating role in the trophic structure of stream fishes due to their influence on resource supply and promotion of the physical heterogeneity of the channel.